Telephone system



April 21, 1931. c. E. BEALE 1,301,301

TELEPHONE SYSTEM Filed April 22, 1929 4 Sheets-Sheet 1 Iii-aim CharlesEdmund Eialb 8 Q h NN o m P m ,w QT w a N M Mn 8 w I m w L m n x mu 7 vEm5 1llll| 3? il V a 3 J gm Mm wv Q|W|- Mm ll. g a h I. .2 mm mm at. ZNUN W.

April 21, 1931. c. E. BEALE 1,801,301

TELEPHONE SYSTEM Filed April '22, 1929 4 Sheets-Sheet 2 A? HERZA.

@ g Irwin-5* $15 EZ'LIF'ZE! Edmund Baal: Q

AprilZl, 1931.. 5 A E 1,801,301

TELEPHONE SYSTEM Filed April 22, 1929 4 Sheets-Sheet 3 Inn-11hr Eh r155Edmund EEEZE 1 1 DE LAY ED 1135 M April 21, 1931.

Filed April 22, 1929 C. E. BEALE TELEPHONE SYSTEM co oa,

4 Sheets-Sheet 4 harlas Edmund Banzai Patented Apr. 21, 1931 UNITEDSTATES PATENT OFFICE CHARLES EDMUND BEALE, OF LONDON, ENGLAND, ASSIGNORTO ASSOCIATED TELE- PHONE AND TELEGRAPH COMPANY, OF CHICAGO, ILLINOIS, ACORPORATION OF- DELAWARE TELEPHONE SYSTEM Application filed April 22,1929, Serial No. 356,952, and in Great Britain June 27, 1928.

The present invention relates to telephone systems and is moreparticularly concerned with final selector switches for use in suchsystems.

i The object of the invention is to provide circuits for all classes offinal selectors which shall be more efficient than those hithertoemployed, having particular regard to the conditions of heavy trafficand other factors met with in modern automatic and semiautomatictelephone networks. These improvements have been attained withoutincreasing the number of relays usually employed and without the use ofspecial con tacts actuated by the switch mechanism other than theoif-normal and cam spring contacts generally in use.

According to one feature of the invention, the ringing relay is mademore efficient by reducing its spring combination to a minimiun.Further, the application of ringing to a called line is suflicientlydelayed to ensure the operation of the cut-off relay and thus preventpremature tripping of the ringing. A feature of the circuits in thisconnection is the arrangement of the rotary shunt relay which alsocontrols the application of ringing current and which is alsore-operated in circuit with the ringing relay to complete the speakingcircuit when the called party replies.

According to another feature of the invention, the supervisory relay ofthe called party is disconnected from the lines whilst impulses arebeing transmitted to the switch in order to prevent any possibility ofthe speaking condensers adversely affecting the impulse accepting relayby reason of discharges and also in order to prevent any possibility ofthe operation of said relay in such circumstances.

A further feature of the invention consists of the guarding of theswitch till a normal position is reached. The release trunk circuit isarranged to be opened momentarily on the release of the calling party toallow other switches in the connection to restore, and thereafter isimmediately re-guarded till the normal position is reached. This isefiected by allowing the relay which normally operates when a busy lineis reached, to re-operate in circuit with the release magnet.

In order that the invention may be better understood, and more readilycarried into effect, a detailed description will now be given of methodsof applying these features, reference being had to the attacheddrawings. It will be understood however, that this is given by way ofexample only and that various modifications may be made in the circuitdetails by those skilled in the art without departing from the spirit ofthe invention.

Referring now to the accompanying drawings, Fig. 1 shows a regular finalselector circuit; Fig. 2 a circuit suitable for P. B. X. subscribershaving from 2 to 10 lines in their group; Fig. 2A a typical testing bankarrangement for connectors such as that shown in Fig. 2; Fig. 3 acircuit for P. B. X. subscribers having groups of from 11 to 20 linesand Fig. 4 provides similar facilities for large groups of lines to P.B. X. subscribers. Referring now particularly to Figure 1, when theswitch is seized over conductors 12 and 13, impulse accepting relay Awill operate over the circuit: earth, back contact and armature 10,lower winding of relay A, springs controlled by armature 11, conductor12, callingloop, conductor 13, springs controlled by armature 14, upperwinding of relay A to battery. Relay A operates and closes the circuitof guard relay B at the front of armature 15. Guard relay B operates andearths the release trunk conductor 15 to guard the switch at armature16; at armature 17 short circuits the lower winding of relay E to makethat relay slow releasing; at armature 18 prepares a holding circuit forthe switching, ringing or busy relays and operates relay C via oilnormal contacts 19; and at armature 20 prepares the impulsing circuit tothe magnets.

The operation of relay C removes earth from the lower winding of relay Dat armature 21 so that this relay does not adversely affect the impulsesby causing the speech condensers to charge and discharge and at the sametime the possibility of this relay operating during the transmission ofimpulses to till -' ture 25 the switch is completely avoided. At thefront contact of armature 22 relay C short circuits its upper winding tomake it slow to release; at armature 23 a circuit for the busy relay Gis prepared; while at armature 24ia holding circuit for itself isprepared so that relay C will remain in the operated position duringimpulsing of the vertical series, when the off-normal springs areoperated. When the calling subscriber dials the next digit of the wantedsubscribers numb r, or alternatively when the register controllerforwards the necessary impulses, relay A will impulse in synchronism andat each restoration will complete circuit: earth, armature and backcontact, armature 2O and'front contact, armature 24; and front contact,armature 25 and back contact, vertical magnet V to battery. The]vertical magnet operates and raisesthe wipers one step each time itoperates. On the first vertical step the off normal springs close, thusmaking circuit of relay C now dependent on the impulsing circuit. duringthe impulsing-due to their slow release feature. V] hen the impulseseries is completed the wipers will be opposite the required level andrelay C will rel-ease following its slow-to-release pause. Belay Ethereupon operates over the circuit: earth, front contact and armature'18, off-normal springs 26, armature 2'2' and back contact, back contactand armature 22, upper winding of relay E to battery; relay E operatesand at arma the impulsing circuit is now transferred to the rotarymagnet R. At armature 28 relay E closes a locking circuit for itselfwhich is independent of relay C. When the next impulse series isreceived, relay A will impulse as before and the rotary'magnet R will beoperated over the circuit: earth, armature 15 and backcontact, armatureand front contact, armature29 and back contact,

armature is and back contact, armature and front contact to the magnetR. A parallel circuit also extends from theback contact of armaturee'land off-normal springs to relay C which operates and renders itselfslow-to-release at armature 22 and at armacalled subscribers cut-0Erelay (not shown) to battery.

Relay H operates and closes a locking circuit foritself at its armature32 and at the the holding Relays B and C hold up.

stores and at the back contacts of armatures 35 and 36 the ringingcircuit is completed. This ringing circuit may be traced from ringingcurrenton conductor 37, upper winding of ringing trip relay F, backcontact and armature-35, armature 33 and front contact, line-wiper 38,called subscribers line, subscribers bell and condenser in series, linewiper 39, front contact and armature 34, armature 33 and back contact,resistance 40 to battery. I 1

Under these conditions the ringing relay F does not operate, and'thewanted subscriber will be signalled. It will have been noticedthat theapplication of ringing current to the wanted subscribers lines isslightly delayed after the switching of relay H due to the releasingtime of relay E and therefore there is no possibility of prematureoperation of relay F, as the wanted subscribers cut-off relay is givenample time to operate and dis connect the line relay. An indication tothe calling subscriber that ringing current is being applied is alfordedby means of the leak condenser 41 which is connected between theoutgoing line and the calling circuit by armature'4c2. 1

As soon as the called subscriber removes his receiver to reply to thecall he places a direct current path across his loop and relay Fthereupon operates and at armature 43 provides a holding circuit foritself from earth at armature 18 in series with the upper winding ofrelay E. Relay E alsooperates in this circuit and completes the talkingcircuit between the two subscribers at the-front contacts of arinatures35 and 36. Back bridge relay D now operates over the called subscribersloopand at armatures 14 and 11 causes the direction of current flow tothe calling circuit from relay A to be reversed. This reversal is usedfor metering and signalling purposes. Conversation may now take place. tmay be noted that the further operation of the calling subscriberscalling device or a momentary operation of the switchhook is'renderedineffective to step the switchby the opening of the impulsing circuit atarmature 4L4.

At the conclusion of conversation the release of the switch takes placewhen the calling subscriber replaces his receiver. Relay A thereuponrestores and at armature 15 opens the circuit of relay B which after itsslow-to-release period also restores. The

locking circuit of relays H, F and E is now opened at armature l8 andthese relays release; also at armature 16 earth is removed from therelease trunk conductor 45 allowing the other switches in the connectionto be released. A circuit is also completed from earth,armature 15 andback contact, armature 20 and back contact, off-normal springs 64,release magnet RM and lower winding of relay G in parallel, to battery.The release magnet RM operates and causes the restoration of the wipersto normal in known manner while the operation of relay G closes acircuit at armature 46 for the re-guarding of the release trunk. Thiscircuit is from earth, front contact and armature 46, back contact andarmature 47 to the release trunk conductor 45. l/Vhen the switch is inits normal position off-normal springs 64 open allowing thedeenerigization of the release magnet and relay G thus removing theguarding earth. The switch may now be taken into use for other calls.

It will have been noticed that when the switch is released the releasetrunk conductor circuit is momentarily opened after relay B restores andbefore relay E restores and relay G operates. This period is long enoughto allow other circuits to restore and the release trunk is thenre-guarded till the switch has restored to normal. This arrangementprevents the switch being taken into use during heavy trafiic periods byanother calling switch whilst it is restoring to normal withoutunnecessarily holding other apparatus.

If the called partly replaces his receiver before the calling party adelayed alarm circuit is closed, and becomes operable after apre-determined time interval if the calling subscriber fails to replacehis receiver. This alarm circuit is from battery through the lamp 52,front contact and armature 48, front contact and armature 49, backcontact and armature 50 of relay D, which restored when the calledsubscriber replaced his receiver, conductor 51 to the delayed alarmarrangements. The glowing of the lamp 52 indicates to the maintenanceoflicer which switch is being held so that if necessary-he can effectthe release of the connection.

The operation of the switch if the desired subscriber is found busywillnow be considered. In this case, as soon as the wipers reach thecorrect contacts the test'wiper 31 will encounter earth andthis willcause the operation of busy relay G via armature 23 and front contactbefore relay O releases. When relay C restores, relay G remains lockedvia the springs controlled by armature 23, front contact and armature 30to earth at armature 18. Switching relay H is unable to operate becauseits circuit is opened at the back contact of armature 30, and relay Etherefore remains energized. At

armature 10 of relay G, earth is removed from the lower winding of relayA and busy flash and tone are substituted, from conductor 53, armature S1 and front contact, back contact and armature 55, front contact andarmature 10, in order to provide a lamp signal in an originating ofiiceas well as a tone, this busy signal may consist of alternate battery andearth periods, the tone being also on during one of these periods.During the battery period, when relay A will restore, battery is alsoconnected to conductor 56 and guard relay B is held from earth, backcontact of armature 15, armature 20 and front contact, armature 29 andfront contact, upper winding of relay B to battery connected toconductor 56.

The calling subscriber hearing the tone or alternatively the operatorseeing the lamp flash if the call is through a manual office, willrelease thereby allowing relay A to restore and relay B then releasesand is followed by relays E and G. The release of the switch then takesplace as previously described. If the subscriber hangs up his re ceiveror if the operator releases, during the battery period of the busysignal relay B remains held till the conclusion of the period when therelease then takes place. This arrangement prevents unguarded periods onjunctions if the call has passed through several exchanges.

Referring now particularly to Fig. 2, when the switch is seized by thepreceding switch, impulse accepting relay A operates over a circuitsimilar to that previously described and at armature 10 extends earth tooperate the guard relay B. The operation of guard relay B earths therelease trunk conductor at armature 11 to guard the circuit, while atarmature 13 it extends earth to operate relay C and further prepares theimpulsing circuit to the magnets at armature 14:. Relay C upon operatingremoves earth from the lower winding of relay D at armature 15, toprevent that relay from interfering with the impulsing and preparesvarious circuits which will be more readily obvious as the descriptionproceeds. Among these relay C prepares a circuit from the test wiper 23to the busy relay G at armature 16 via the resistance 17 and at armature18 disconnects the circuits to relay E and short circuits its own lowerwinding thereby rendering it slow-to-release.

When the calling subscriber proceeds to dial the next digit of thedesired subscribers number, relay A will impulse in synchronism, whereatearth impulses are connected to the vertical magnet thus causing theshaft and wipers to be raised to the predetermined level. It will benoticed that relays B and C hold up during impulsing due to their slowreleasing features. At the completion of the vertical train of impulses,relay C will release after its slow period so that the following circuitis now completed to relay earth, armature. 13 of relay B, operatedolfnormal springs 19, back contacts of armaiures 20 and 18, lowerwinding of relay E to battery.

Relay .E thereupon operates and at its armature 21 provides a lockingcircuit for itself which is independent of relay C; at armature 22 theimpulsing circuit is transferred to the rotary magnet R. l Vhen the nextseries of impulses is received, relay A will again impulse as before andthe rotary magnet and relay C will nowbe operated in parallel, whereuponthe wipers to be stopped round to the first contact of the groupdialled. It will be noticed that do the period that the wipers arestepping round the bank, a circuit is prepared to relay G at armature 16of relay C, as previously described, and should the private wiper 23encounter earth while passing over busy connections, the limitation ofcurrent in the circuit due to the comparatively high value of resistance1? causes relay G to make its armature 24 only, the operation of whichis in effective at this stage.

At the conclusion of the impulse series, the Wipers will be resting onthe first line in the group dialled. and should this be busy, test wiper23 will encounter earth, and wiper 25 will encounter battery connectedthrough a resistance, so that it will be seen when relay C releases atthe completion of the rotary series of impulses, the resistance 17 isshort circuited at armature 26, thus enabling relay G to fully operateover the circuit: earth at armature 13 of relay B, light armature 24,resting contacts of armatures 16- and 26, upper winding of'relay G tobattery. A typical view of the testing bank arrangement referred to, isshown in detail at the bottom left hand corner of the figure. Thehunting start relay HS will now be energized from earth at wiper 23,armature 16 and back contact, armature 27 and front contact, upperwinding of relay HS, armature 28, wiper 25, resistance similar to 38 tobattery, after which a locking circuit is provided over the path: earthat armature 13 of relay B, armature 29, interrupter springs 30, lowerwinding of relay HS to battery. The operationof relayHS also completes acircuit to the rotary magnet R from earth at armature 13 of relay B,armatures 31 and 22, winding of the rotary magnet R to batter, andparallel there-- to over the operated elf-normal springs 19, upperwinding of relay C to battery. Both relay C and the rotary magnet H aretherefore operated in parallel, and as soon as the rotary interruptersprings 30 break, the circuit of the lower winding of relay HS isdisconnected causing it to release, and in turn breaks the circuit tothe rotary magnet R and relay 0 at armature 31, so that the wipers willbe moved on to the next set of contacts. It will be appreciated thatrelay C will not release immediatelyits circuit is disconnected, due toIiLS slow releasing feature, and should this next set of contacts testbusy, earth will be encountered on wiper 23 and via the strapped testingbank contacts to wiper 25 so that a circuit is thus connected for relayHS from earth at wiper 25, armature 28, upper winding of relay HS,armature 32, interrupter springs '30, lower winding of relay H tobattery. The hunting start relay HS is therefore operated over both,windings in series and the rotary inagnet and relay C are againenergized over the circuit previously described. This cycle ofoperations will continue so long as the wipers 23 and 25 encounter busy,contacts, and the'wipers will accordingly step from contact to contactuntil afree trunk is found.

lnthe event of all the lines testing busy, the switch wipers willeventually reach the last contacts in the group, which it will be notedare not strapped, whereupon wiper 23 only will encounter earth, and itwill be appreciated that relay HS will not re-operate and the circuit torelay C is now definitely opened. After a-short pause relay C willrelease and at armature 16 the locking circuit to relay C will again betransferred to earth at armature 13 of relay B; The so-called busy flashand hold circuits thereby eX- tended over conductors 36 and 37 on relayB and function in similar manner to that described more fully inconnection with Figure 1. Assuming however, that a free trunk isencountered in the particular group dialled, wipers 25 and 23 willencounter battery via the cut-off relay of the line selected. Corrsequently, relay -HS will not re-operate and relay G which has beenholding from the earth on wiper 23 also releases, so that upon therelease of relay C after its slow period a circuit may now betraced forrelay H from earth at armature13 of relay B,upper winding of switchingrelay H, back contacts of armatures 2? and 16, wiper 23, to battery viathe winding of the cut-off relay. Relay H operates over the circuitdescribed and closes a locking circuit for itself at its armature 33 toearth at armature 13, and also connects a direct earth at armature 20 towiper 23 to ensure the full operation of the cut-off relay and to markthe selected line busy. The cirare cuit to the slow releasing relay E isalso opened at armature 20 of relay H, so that after a short pause relayE releases and ringing current is thereby connected to the calledsubscribers line substantially as described in connection with Fig. 1.

When the called subscriber removes his receiver to answer the signal hisline is looped and the ringing relay F operates in known manner, thuscompleting a circuit for its lower locking winding in series with theLil lower Winding of relay E. The operation of relay E, at this stagedisconnects the ringing feed and causes the speaking connection betweenthe two subscribers to be completed at the front contacts of armatures34 and 35, while the called subscribers loop closes a circuit for theback bridge relay D which operates and reverses the. direction ofcurrent flow in the calling loop for metering or supervisory purposes.

It will be appreciated by those familiar with the art, that thesupervision and release of the connection is substantially as describedin connection with Figure 1. 7

Referring now particularly to Fig. 3, when the connector is selected byapreceding switch, the impulse accepting relay A operates in knownmanner and at armature 10 extends earth to operate the guard relay B.The operation of guard relay B connects earth to the release trunkconductor 12 at armature 11 to guard the switch, while at armature 13earth is extended to relay C by way of resting contacts of off-normalsprings 14, upper winding of relay C to battery and also to relay E via'armatures 15 and 16 winding of relay E to battery. The operation ofrelay E controls the extension of ringing at its armatures 17 and 18,while relay G prepares a holding circuit for itself at armature 19 andalso connects both windings of shunt fifeld relay G in parallel over thecircuit earth at armature 20 of relay B, armature 22 and front contact,armature 23 and front contact, left hand winding of relay.

G, interrupter springs 24 of rotary magnet R to battery and via armature22 and front con-tact, right hand winding of relay G, interruptersprings 24 to battery. Relay G operates and prepares a circuit for theinitial rotary kick when relay C releases. When the calling subscriberproceeds to dial the next digit of the desired number, relay A willimpulse as previously explained and the first impulse will follow thepath, earth at armature 10 of relay A, operated armatures 25 and 19,winding of vertical magnet V to battery, so that the shaft and wiperswill be raised one step and the off-normalsprings 14 will be operated,thereby causing the initial energizing circuit of relay C to bedisconnected, thisrelay however does not release immediately'du'e to itsslow-to-release feature and when the next impulse is transmitted thefollowing parallel path may be traced to relay C, earth at armature 10,armatures 25 and 19, operated off-normal springs 14, upper winding ofrelay C to battery. Consequently, relay C will be heldoperated duringthe remainder of the vertical impulses, and when the wipers of theswitch finally arrive opposite the level dialled, relay C will releaseafter a short pause, thereupon operating the rotary magnet over thecircuit:

earth at armature 20, armature 22 and back contact, front contact andarmature 26, winding of rotary magnet R- to battery. It will beappreciated therefore that the wipers of the switch will be moved on tothe first set of contacts and the circuit of both windings of relay Gwill be opened at the rotary interrupter springs 24. Assuming now thatthe first set of bank contacts test busy, wipers 27 and 28 will bothencounter earth so that relay G will re-operate via both its windings inparallel over the circuit: earth, wiper 27, back contacts of armatures29 and 30, right hand winding of relay G interrupter springs 24, tobattery and earth, wiper 28, armatures 31 and 32, resting contacts ofcam springs 33, left hand coil of relay Gr interrupter springs 24, tobattery. Accordingly, the shunt field relay G operates and locks up overits armatures 34 and 35 to earth at armature 20, whereupon the wiperswill be moved on to the next set of contacts by a similar circuitarrangement to that already described.

It should be mentioned that armatures 34 and 35, besides completing alocking circuit for relay G, also short circuit the windings of theswitching relays HA and HB until the correct time arrives. This shortcircuit may be traced from earth at armature 20, ar matures 34 and 35,through the windings of relays HA and HB and armatures .36 and 37respectively, operated contacts of off-normal springs 14, restingcontacts of cam springs 33 and back to earth at armature 20. Assumingnow that testing wiper 28 encounters a free trunk, the busy earthpreviously mentioned will be replaced by battery via the cut-off relayof the called subscriber, so that the circuit is only completed for theright hand winding of relay G, and as is well known to those skilled inthe art, the magnetic flux produced in the right hand coil of shuntfield relay G will now pass through the closed iron circuit provided bythe core of the deenergized left hand winding, thereby diverting theoperating power of the relay so that it becomes in-operative. The shortcircuiting earth is accordingly removed from the winding of relay HA atarmature 34 of the relay G and the following operating circuit iscompleted earth at armature 20, resting contacts of cam springs 33,operated contacts of off-normal springs 14, armature 36, winding ofrelay HA, left hand winding of relay G, interrupter springs 24 tobattery. The operation of relay HA completes various circuit functions,among which is the connection of a direct earth to wiper 28 overarmatures 32 and 31, thereby ensuring the operation of the cut-ofi'relay of the called subscribers line switch and also marks the trunk inuse busy to other callers.

The circuits to relay HB and the testing wiper 27 are opened atarmatures 37 and 29 respectively, and the ringing circuit to the calledsubscriber is prepared at. arniatureS 1 rent to the called line at itsarmatures 17 and 18, the circuit details of which will now be generallywell recognized. When the called subscriber removes his receiver toanswer the call his lines are looped via the switchhook spring and theringing relay F is operated in known mannerand completes a circuit forits upper locking winding in series with. relay E. The operation ofrelayE disconnects the main ringing circuit and also completes thespeaking connection betweenthe calling and called parties at armatures17 and 18. The closure of the loop via the called subscribers instrumentcauses the back bridge relay D to I operate, thereby reversing thedirection of current flow around the calling loop for metering orsupervisory purposes.

Upon the release of the switch, earth will be extended over restingcontacts of armatures 10 and 25, operated off-normal springs 14, windingof relay C and the release magnet Z in parallel to battery, thus causingboth to operate, so that the switch will be guarded during its releasingperiod from earth at operated armature 41 over the release trunkconductor 12. Individual supervision and a delayed alarm scheme are alsoincorporated in a similar manner to that already fully described inFig. 1. p 1

Should all the lines in the group test busy, the switch wipers willcontinue to rotate until they pass beyond the last contact of the group,whereupon cam springs 33 will be operated thereby disconnecting testwiper 28, so that the circuit to the left hand coil of re lay G isopened and the relay will not reoperate. Moreover, the operating circuitto both switching relays HA and HE is also opened at the left handcontacts of the cam springs 33 and the busy hold circuit is completed tothe lower winding of relay B while at the centre contacts of the camsprings, busy flash and tone is connected to the lower winding of relayA, via armature 42 of relay B. The function of the busy circuit is morefully described in the foregoing description of Fig. 1.

for the left-hand winding-of relay G. Re-

lay G will restore, as previously explained and remove theshort-circuiting earth from the windings of relays HA and HB. Re-

lay HA does not operate since its winding is short-circuited by theearth encountered by wlper 28. Relay HB, however, operates over acircuit extending from earth at armature 20, resting contacts of camsprings 33, op-

rupter contacts 24. The operation of relay,

HB completes various circuit functions among which is the connection ofa direct earth to wiper 27 over armatures 30 and 29 to insure theoperation of the called subscribers cut-off relay and to mark the trunkbusy. Relay HB also connects up the upper set of talking wipers, opensthe circuit of relay HA at armature 36 and disconnects wiper 28 atarmature 31. The holding circuit ofrelay E is opened at armature 16 andthat relay releases and completes the ringing circuit as previouslydescribed. The operations involved'when the call is answered and theconnection is released are the same as those described for a callcompleted over wiper 28.

Referring now. particularly to Figure 4, when the switch is selected bya preceding switch, impulse accepting relay A operates over the callingloop in known manner and at armature 10 extends earth to operate theguard relay B. The operation of guard relay l3,'earths the release trunkconductor 11 at its armature 12 to guard the switch; prepares a circuitat armature 13 for the driving magnet DM, and further completes acircuit to relay E over the path: earth, armature 14, back contact ofarmature 16, winding of relayE to battery. The operation of relay Eopens points in the ringing circuit at its armatures 17 and 18 and alsoprepares the 7 initial stepping circuit for the automatic rotation ofthe rotary switch at armature 19. Normally on this type of switch thesubscriber would dial one impulse only, and when relay A releases uponthe reception of this impulse, relay C is operated via earth at armature14' of relay B, resting springs of armatures 15 and 20, upper windingof'relay C to battery. Relay G operates and completes a circuit to itslower winding from earth at armature 14 ofrelay B,armature 19, homecontactof bank 20, wiper 21, armature 22 and front contact, lowerwinding of relay C to battery and parallel thereto via frontcontactandarmature :13 of relay B, interrupter H springs 23, winding of drivingmagnet DM to battery. 7

The, driving magnet therefore energizes and opens-its own circuit at theinterrupter springs 23, so thatthe wipers will be moved on to the nextset of contacts in a manner which is well known. Should the next set ofcontacts test busy, earth will be extended via wiper 21 over a similarpath to that previously traced, so that the driving magnet will againenergize, while relay 0 remaini held during its open circuit periodsunder connected at armature 24, to prevent this re-' lay flicking duringimpulsing.

Assuming now that wiper 21 eventually en counters an idle line, batteryin place of earth is found connected to the testing contact bank 20'sothat the magnet is not re-operated and relay C is short circuited, thuscausing this relay to release whereupon a circuit is then completed tothe switching relay H from earth at armature 14 of relay B, frontcontact and armature 19, upper winding of switching relay H back contactand armature 22, wiper 21, to battery via the cut-off relay of the lineselected. Relay H operates its armature 25 over this circuit andcompletes the circuit for its lower locking winding to earth at armature14 of relay B, whereat relay H operates fully and at armature 15connects a direct earth to the testing wiper 21 in order to guard theconnection and ensure the op eration of the cut-elf relay of the lineselected. It will be noted that the holding circuit to relay E is openedat armature 16, and after a short pause due to its slow feature thisrelay will release, whereupon ringing current will be connected to thecalled subscribers instrument over the circuit, ringing feed overconductor 26, winding of ringing relay F, armatures 27 17 and 28, wiper30 and bank contact, called subscribers instrument, bank contact andwiper 31, armature 32, armature 18 and back contact to ring returnbattery. In response to the ringing circuit thus completed the calledsubscribers bell will ring, and when he removes the receiver'to answerthe call,thelinewi"ll be looped via the switch hook springs, and theringing relay F will be operated as described in connection with theprevious figures. The operation of relay F completes the circuit for itslower locking winding at armature 33 in series with relay E, and thelatter relay operates and completes a speaking connection between thecalling and called subscribers at armatures 17 and 18. At this periodthe back bridge relay D is operated over the called subscribers loop andhere again current flow in the calling loop is reversed for metering orsupervisory purposes.

In the event of all the lines in the QTOU} testing busy, the wipers willbe automatically rotated to the 25th contact, or if double banks areused the 50th contact, whereupon relay G willbe operated in series withrelay H over the circuit: earth, armature 14 and front contact, armature19, upper winding of relay H, back contact and armature 22, testingwiper 21, last bank contact in the group, upper winding of relay G tobattery. Relays G and H operate in this circuit and cause a busy flashand tone over conductor 34, to be extended by way of armatures 35 and 36to the lower winding of relay A, while a busy hold circuit is connectedvia conductor 37, upper winding of relay B, armature 38, to earth atarmature 39 of relay B.

The function of the busy flash and hold circuit has already been fullydescribed in connection with the previous figures, and suflicient isindicated herewith to enable its application to be readily appreciatedfor this particular circuit. It should be mentioned that although thenecessary circuit functions to produce a ringing condition have beenperformed, the last contacts in the group are open, so that wipers 30and 31 are switched through to a dead line and consequently the ringingcircuit is ineffective.

On the release of the connection when the calling subscriber replaceshis receiver, relays A and B are restored, and consequently earth isremoved from the main holding circuit at armature 14 of relay B, therebyreleasing the various relays which have been locked thereto. It will beseen that when all the; relays have released, a homing circuit will thenbe completed from earth at the back contact and armature 14, homingplate 40, wiper 41, back contact and armature 13, interrupter springs23, winding of driving magnet DM to battery, and parallel thereto viathe lower winding of relay G to battery.

The self interrupter circuit thus connected will cause the wipers of theswitch to be stepped to the first bank contacts whereupon earth via thehoming plate is disconnected and the wipers come to rest in the homeposition. It will be noticed during the period that the'wipers arerotating to the home position, relay G will be operated over its lowerwinding, and the release trunk conductor 11 will be guarded over thecircuit: earth at armature 42, back contact and armature 43 to conductor11 thereby ensuring that the switch mechanism is completely restored tonormal before the switch is freed for engagement on other calls.

What I claim as new and desire to secure by Letters Patent is 1. In aconnector switch having access to subscribers lines, a switching relayenergized responsive to the extension of a connection to an idle line,and means including a second relay controlled by said switching relayfor delaying the application of signalling current to the called linefor a predetermined time after the line is connected with.

2. In a connector switch having access to subscribers lines, a switchingrelay energized responsive to the extension of a con nection to an idleline, and means including a relay energized during the setting of theswitch and released responsive to the operation of said switching relayfor delaying gized responsive to the extension of a con-' nection to anidle line, arelay through which the application of signalling current tothe called line for a predetermined time after the line is connectedwith.

3. In a connector switch having access to subscribers lines, a switchingrelay enerized res onsive to the extension of a connection to an idleline, a slow-to-release relayreleased responslve to the operatlon ofsaid switching relay for completing the'signalling circuit of theswitch, and means for re-operating said slow relay to open saidsignallingcircuit when the call is answered.

5. In a connector switch having access to subscribers lmes, a switchingrelay enerringing current is applied to a called line, said relayoperating responsive to the answering of the call, a. cut-off relay forcon trolling theapplication of ringing current to the called line, aninitial operating circuit for said cut-off relay including normallyclosed contacts of said switching relay, and a subsequent operatingcircuit for said outoff relay including operated contacts of said secondrelay.

6. In a two-directional connector switch equipped with primary andsecondary step-- ping magnets, a relay energized during the setting ofthe switch for effecting a changeover from the primary magnet to thesecondary magnet, a switching relay energized responsive to theextension of a connection to an idle line, and means controlled by saidswitching relay for releasing said, first relay.

7. In a two-directional connector switchequipped with primary andsecondary stepping magnets, a slow-to-release relay energized during thesetting of the switch for eiiecting a changeover from the primary magnetto. the secondary magnet and for opening the signalling circuit of theswitch, a switching relay energized responsive to the extension of aconnection to an idle line, and means controlled by said switching relayfor releasing said slow relay to complete said signalling circuit.

8. In a two-directional connector switch equipped with primary andsecondary stepping magnets, a slow-torelease relay energized during thesetting of the switch for effecting a changeover from the primary magnetto. the secondary magnet and for opening the signalling circuit of theswitch, means for releasing said relay responsive to'the extension of aconnection to an idle line, and means for re-operating said relayresponsive to the answering of the call.

9. In a connector switch, a relay through which ringing current isapplied to a called line, a second relay for disconnecting the ringingcurrent from the called line, and an operating'circuit for said secondrelay including the windings of both relays in series.

10. In a connector switch, a relay through which ringing current isapplied to a called line, a second relay for disconnecting the ringingcurrent from the called line, means for operating said first relayresponsive to the answering of the call, and means controlled by saidfirst relay for operating said second relay.

11. In a connector switch, a double wound relay, a circuitincluding onewinding of said relay for applying ringing current to a called line,asecond relay for opening said circuit, and means for operating saidsecond relay in series with the other winding of said first relay. p I

12. In a connector switch, a double wound relay, a circuit including onewinding of said relay for applying ringing current to a called line, asecond relay for opening said circuit, means for operating said firstrelay responsive to the answering of a call, and means controlled bysaid first relay for connecting its other winding in series with saidsecond relay to energize both relays,

13. In a connector switch, a relay through which ringing current isapplied to a called line, a second relay for disconnecting the ringingcurrent from the called lineand'for completing a talking connectionthereto,-a circuit for energizing both of said relays in series, andmeans controlled by said first relay for completing said circuit.

14. In a connector switch two relays, a ringing circuit including awinding of the first relay and contacts of the second relay, and anoperating circuit for thesecond re lay including a second winding ofsaid first relay and contacts controlled by that relay.

'15. In a two-directional connector switch equipped with primary andsecondary magnets, a relay energized at the end of the primary operationof the switch for effecting a changeover from the primary magnet to thesecondary magnet, means for releasing said relay when a connection isextended to an idle line, and means for re-operating said relayresponsive to the answering ofthe call.

16. In a'two-directional connector switch equipped with primary andsecondary magnets, a relay energized at the end of the primary operationof the switch for effecting a changeover from the primary magnet to thesecondary magnet, means for releasing said relay when a connection isextended to an idle line to complete a circuit for signalling over theline, and means for reenergizing said relay responsive to the answeringof the call to open said signalling circuit and to complete a talkingconnection with the line.

In testimony whereof I have signed my name at Liverpool this th day ofMarch,

CHARLES EDMUND BEALE.

